Have you read series of articles from extrawurst about his experience of using vibe.d for game server? http://forum.dlang.org/post/dxcruptyfxsaauihzknw@forum.dlang.org
I don't think there are many straightforward advantages from vibe.d architecture for your specific use case but there are no drawbacks either. It is pretty simple and you get some utility modules implemented on vibe.d base. Also I doubt using worker thread with naive locking system will do any benefit, can possibly be even worse than simple single-threaded approach. Multithreading is good when you can minimize locking as much as possible.